1. Field of the Invention
The invention relates to a device for read-out and erasing information from storage sheets which are conveyed to the device in a cassette, with a cassette holder, means for opening the cassette, a scanner for reading the stored information, an erasing device for erasing the stored information and a transport device which transports the storage sheet past the scanner and the erasing device.
2. Description of the Related Art
U.S. Pat. No. 5,665,976 discloses a device which can be used to read-out and erase stimulable phosphor sheets. First, the sheets are transported past a scanner and thereafter past an erasing station. In the erasing station, the sheet is irradiated with light of a predetermined wavelength which does not interfere with the scanning process. After the sheet has passed the erasing station, the transport direction is reversed, and the sheet is moved past the erasing station for a second time. Since the second erasing process takes place after the scanning operation, light of a different wavelength can be used.
To scan a sheet which has been removed from the cassette, the sheet initially has to be either centered or at least moved to a pre-defined position. This operation requires physical space. Typically, the sheet is removed from the cassette, then oriented and subsequently conveyed to the scanner, meaning that the scanner and the cassette are separated by approximately the length of one sheet. A sheet can be scanned accurately only after having been precisely oriented.
A scanner for scanning storage sheets typically has a small scan slit opening. Respective transport roller pairs are arranged in close proximity before and after the scan slit opening, respectively. This arrangement ensures a uniform speed of the sheets past the scan slit opening. In the device disclosed in U.S. Pat. No. 5,665,976, the sheet moves from the roller pair located after the scanner to the erasing device. As clearly indicated, an additional roller pair which grips the sheet is located after the erasing device to pull the rearward end of the sheet past the erasing device. Consequently, the arrangement illustrated in U.S. Pat. No. 5,665,976 requires at least three roller pairs making contact with the sheet after the sheet is removed from the cassette.
In conventional devices, the presence of at least three transport roller pairs and the required separation between the cassette and the scanner necessitate long transport paths for the storage sheets. In order to nevertheless make the housing compact, the transport paths are typically folded, necessitating small bending radii.
It is an object of the invention to provide a device for read-out and erasing information from storage sheets which ensures a gentle treatment of the storage sheets. Small radii on the transport paths and a large number of transport roller pairs should also be avoided.
The object is solved by an arrangement providing an erasing device between a cassette holder and a scanner. By locating the erasing device between the scanner and the cassette holder, the device requires only two transport roller pairs. Accordingly, abrasion and wear of the storage sheets can be reduced significantly. Moreover, the section of the transport path provided for erasing the storage sheets can also be used for aligning the storage sheets. This arrangement provides an extremely compact construction and a very short transport path.
The respective transport roller pairs are arranged before and after the scan slit opening, respectively. For the read-out process, the storage sheet is removed from the cassette by a transfer device, moves past the erasing device which is not activated, and is then transported by the transport roller pairs past the scanner, until the storage sheet is held only by the transport roller pair located after the scan slit opening.
For erasing, the sheet is transported in the opposite direction. The transport speed during the erasing process can be greater than during the scanning operation.
The cassette holder, the erasing device and the scanner are vertically stacked one on top of the other. The cassette holder is oriented in such a way that the storage sheet can be removed downwardly from the cassette and conveyed with its forward marginal region directly to the transport roller pair arranged above the scan slit opening. The storage sheet can thus be guided over the entire transport path from the cassette past the erasing device and the scanner essentially without changing direction.
With this advantageous arrangement, the scanning process can already begin when a portion of the storage sheet is still located inside the cassette. Likewise, the erasing process during transport of the sheet in the reverse direction ends after a major portion of the storage sheet is already positioned inside the cassette.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.